The present invention relates to a method for manufacturing a semiconductor device; and, more particularly, to a method for manufacturing an aluminum oxide in the semiconductor device by using a modified trimethyl aluminum (MTMA) as aluminum source material.
As is well known, a semiconductor memory device has a higher degree of integration because of downsizing through micronization. However, there is still a demand for downsizing the area of the memory cell, under increased transistor and circuit speeds and improved reliability. Demands for increased density, performance and reliability require the formation of device features with high precision and miniaturization. To meet the demands, it is necessary to increase the capacitance of a capacitor and improve the gate dielectric film which is applied to the DRAM and logic devices. In an attempt to solve a requirement, various researches have been made to employ the high dielectric materials for a capacitor thin film and a gate dielectric film.
Aluminum oxide (Al2O3) is typically used among high dielectric materials for the capacitor thin film and the gate dielectric thin film because aluminum oxide has good oxidation resistance and thermal stability. Furthermore, it can be used as a hydrogen barrier to prevent hydrogen diffusion.
Aluminum oxide can be formed by using a method such as an atomic layer deposition (ALD). The manufacturing steps are as follows: setting a wafer in a chamber; heating up the wafer to 200xc2x0 C. to 450xc2x0 C.; supplying aluminum source material into the chamber; permitting nitrogen gas (N2) to flow into the chamber and purging the chamber for vacuum status in order to sweep off unreacted aluminum source material or by-product; supplying an oxygen source material into the chamber; and permitting nitrogen gas to flow into the chamber and purging the chamber again for vacuum status in order to sweep off unreacted oxygen source material or by-product. The intended thickness of the aluminum oxide film is obtained by repeating the steps listed above.
In a conventional method for manufacturing the aluminum oxide film in the semiconductor device, trimethyl aluminum (TMA) and water (H2O) are mainly employed as the aluminum source material and the oxygen source material, respectively. TMA has a high vapor pressure and the difference between the boiling and melting points are very small. Therefore, it has drawbacks of strong explosiveness and inflammability when it is exposed in the atmosphere. Thus, TMA is not appropriate as the aluminum source material for manufacturing the aluminum oxide film for various uses in the semiconductor device.
It is, therefore, an object of the present invention to provide a method for manufacturing an aluminum oxide film by using modified trimethyl aluminum (MTMA) as an aluminum source material because it is stable in the atmosphere.
In accordance with one aspect of the present invention, a method for manufacturing an aluminum oxide film for use in a semiconductor device is provided. The method comprises the following steps: a) preparing a semiconductor substrate and setting the semiconductor substrate in a reaction chamber; b) supplying modified trimethyl aluminum (MTMA) as an aluminum source into the reaction chamber so that it can be absorbed on the semiconductor substrate; c) discharging unreacted MTMA or by-product through a first discharge pump by flowing nitrogen gas into the reaction chamber and purging the chamber for vacuum status; d) supplying an oxygen source into the reaction chamber so that it can be absorbed on the semiconductor substrate; and e) discharging the unreacted oxygen source or by-product through a second discharge pump by permitting nitrogen gas to flow into the reaction chamber and purging the chamber for vacuum status.
In accordance with another aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method comprises the following steps of: a) preparing an active matrix with isolation regions, a substrate, gate line, gate oxide and a first insulating layer; b) forming a buffer layer and a first conductive layer on the active matrix; c) forming a dielectric layer of aluminum oxide (Al2O3) on the first conductive layer by using an ALD method, MTMA being used as aluminum source; d) material obtaining a capacitor structure by forming a second conductive layer on the dielectric layer and patterning the second conductive layer, the dielectric layer, the first conductive layer and the buffer layer; e) forming a hydrogen barrier layer on the capacitor structure; f) forming a bit line and a local interconnection after depositing a second insulating layer; and g) forming a passivation layer on the bit line, the local interconnection and second insulating layers.